Automatic refrigerator defroster



1955 H. w. GOODHART AUTOMATIC REFRIGERATOR DEFROSTER Filed Feb. 25, 1953U A M m Y B M H 2 4 a m 5 6 4 14 5:0 4 H Ml! nw z w 0 TCINIJ T 7 m 1...\un W w. m 7% 3T/J\ -3 li f a -3 2 United States Patent 2,722,808AUTOMATIC REFRIGERATOR DEFROSTER Harry w. Goodhart, Baltimore, Md.

Application February 25, 1953, Serial'No. 338,639

3 Claims. (Cl. 62-103) This invention relates to means for defrostingthe freezing compartment of refrigerators and deep freeze boxes, and isparticularly well adapted for use in preventing the layer of ice formingfrost from forming on the inner wall of a deep freezer box, without thenecessity of raising appreciably the temperature of the food stored inthe box or its removal therefrom.

The freezing compartment of the box is usually kept at a temperaturebelow the freezing point of water and the moisture deposits on the top,bottom and sides of the compartment and forms frost. At this frostaccumulates it forms a layer of ice that, due to its insulating effect,reduces the efficiency of the apparatus for reducing the temperature ofthe freezing compartment from time to time.

The general practice heretofore in defrosting the freezing compartmentof a deep freeze box has been to stop to melt, this takes considerabletime and allows the temperature of the foods stored therein to riseconsiderably while the box is being defrosted. It has also been thepractice to scrape the frost free from the walls of the freezingcompartment and then remove the scraping from the box. Another methodhas been introduced incorporating a heating unit embedded in a plasticcovering, but this method aside from reducing the efficiency of thecooling medium merely broke the bond of the layer ice from the face ofthe plastic covering and required the shell of ice to be lifted out ofthe box as a unit. Practically all the methods mentioned required thatthe foods be removed from the box so the slop from the melted ice couldbe mopped up before it became frozen again. All of the methods mentionedallowed the temperature of the foods to rise and become warm while thiswas being done.

The present invention contemplates a simple and practical freezing unitdefroster whereby the layer of iceforming frost will form on a screen orperforated plate placed within the freezing compartment but spaced awayfrom the regular compartment wall, with a heating unit spaced betweensaid screen or plate and the compartment wall to periodically andautomatically release the frost from the screen and compartment wall inthe form of water, and to drain same to the outside of the deep freezerat predetermined intervals.

The invention has for an object the provision of a new and improveddefrosting apparatus for a deep freeze box that will be automatic in itsdefrosting operation and provide means for carrying off the liquidmedium after the defrosting cycle has been completed.

Another object of this invention is to provide a new and improvedportable defrosting unit for placement in a deep freeze box, comprisinga spacer screen or plate positioned adjacent the inner wall of a deepfreezer box and a heating unit placed between the inner wall and thespacer.

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Other objects will become apparent as the invention is more fully setforth.

For a clearer understanding of the invention and its objects, referenceis made to the accompanying drawings, wherein a particular form of theinvention is disclosed. These drawings when used in conjunction with thefollowing description illutrate such form by way of example, while theclaims emphasize the scope of the invention.

In the drawings:

Figure 1 is a plan view of a deep freezer with the lid in closedposition, embodying this invention;

Figure 2 is a plan view similar to Figure 1 with the lid open;

Figure 3 is a sectional view taken along line 33 of Figure 2; and

Figure 4 is a diagram indicating the automatic electrical control of thedefrosting system.

Similar reference numerals refer to similar objects throughout thedrawings.

In the construction shown in the drawings a casing 10 comprising anouter wall 11 and an inner wall 12 forming an enclosure for therefrigerating tubes 13 which are attached to the inner walls 12. Thehollow space between the outer and inner walls is packed with one of theconventional insulating materials to prevent losses through the walls.The face 14 of the inner wall 12 is provided with studs 15 to supportthe screen or perforated plates 16 and to keep them in spacedrelationship with the wall 12. A heating unit element 17 is attached tothe face 14 of the inner wall 12', between the inner wall 12 and eachscreen or perforated plate 16. A cover 18 is attached to the top of thedeep freezer by hinges 19. The freezer is preferably mounted on legs 20.The screen or perforated plates 16 and heater units or elements 17 arepositioned around the walls 12 and the water from the melting iceforming frost drips down and along the spouting 21 which is pitchedtoward a discharge pipe 22 and through the trap 23 and out the drainpipe 24 to the outside. The heating units 17 are also used to defrostspouts 21.

Suitable electrical circuits for the automatic control of the defrostingapparatus are shown in Figure 4. The time clock shown at 30 may be ofany suitable type which may be set to control the circuits at periodicintervals. In the diagram the time clock is shown as having a switch arm31 connected to a wire 32 which leads from one supply line 33. In oneposition of the switch arm 31 it engages contact 34 which is connectedto the lead 28 that goes to the heating units 17. The other lead 28agoing to the heating units is connected to the other supply line 33a. Inthe other position of the time clock switch arm 31 it engages a contact35 which connects by wire 36 to relay winding 30. The other side of therelay winding is connected by wire 41 to the supply line 33a. One sideof the compressor motor M1 is connected by wire 42 with supply line 33a;the other side of motor M1 is connected by wire 43 through thermostaticswitch 46 with one contact of relay switch 44, the other contact of therelay being connected by wire 45 with supply line 33. The usualthermostatic switch 46 is inserted in the wire 43 for thermostaticcontrol of compressor motor M1, for controlling and maintaining thedesired refrigerating temperature.

In normal operation the switch arm 31 of the time clock is in engagementwith contact 35, thus breaking the circuit to the heating elements 17and also closing the circuit relay 39 (from wire 36 through the windingof the relay and wire 41 at supply line 33a). The relay energized,closes the circuit at its switch 44, and thus closes the circuit ofcompressor motor M1 (supply line 33, wire 45, relay switch 44, wire 43,motor M1, and wire 42 back to supply line 33a).

During the normal operation, when refrigerant is being circulatedthrough refrigerating tubes 13, the air will be cooled not only bycontact with the screen or perforated plate section 16, but also bydirect contact with the inner walls 12 to which the refrigerating tubes13 are directly connected.

When the time clock operates to defrost the refrigerating unit, theswitch arm 31 is thrown to the position shown in Figure4. The circuit tothe motor M1 is thus broken and circulation of the refrigerant isstopped. By stopping the circulation of refrigerant it results that theheat supplied to the refrigerating unit for purposes of defrosting willnot be carried away by the circulating refrigerating medium, to otherparts of the system where goods are being cooled.

At the same time that the circuit to the compressor motor M1 is opened,the circuit leading to the heating elements 17 is closed, and heat isthus applied to the screen and perforated plates 16 from the heatingelements. The heating elements being in highly efficient conductiverelation to the inner wall 12 and the screen or perforated plates 16,the supplied heat is substantially evenly distributed and the depositedfrost is quickly and evenly melted.

The time clock will be set to apply the heat and stop circulation of therefrigerant for a period suflicient to thoroughly defrost, and then thetime clock will again operate its control switch to break the circuit tothe heating elements and again close the circuits to the refrigerantcirculating motor M1.

The time controlling system is shown as a matter of preference and notas a limitation, as it is appreciated that other forms of controls maybe utilized, including manual operation, or actuattion by any othersuitable and conveniently usable determining factor that indicates theneed for defrosting.

While but one general form of the invention is shown in the drawings anddescribed in the specification, it is not desired to limit thisapplication for patent to this particular form as it is appreciated thatother forms of construction could be made that would use the sameprinciples and come within the scope of the appended claims.

Having thus described the invention, what is claimed l. A refrigeratingsystem having a refrigerating unit comprising an inner and outer wall,refrigerating tubes positioned inbetween said walls, means forcirculating a refrigerating medium through said refrigerating tubes, aheat insulating filling in the space between said walls, a foraminatedscreen suspended outwardly from said inner wall, and electrical heatconducting units suspended between said inner walls and foraminatedscreen to defrost the unit at predetermined intervals.

2. A refrigerating system as set forth in claim 1, and having a gutterpositioned under said screen and heat conducting units to carry off thewater drippings from said screen and inner wall.

3. A refrigerating system as set forth in claim 2 having means forcontrolling the passage of refrigerating medium through saidrefrigerating tubes and heating said heat conducting units atpredetermined intervals.

References Cited in the file of this patent UNITED STATES PATENTS2,515,294 Cowgill July 18, 1950 2,524,465 Morrison Oct. 3, 19502,601,466 Thomas June 24, 1952 2,641,112 Mufiiy June 9, 1953

